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Oblivion | UltraSonic Studios

Discussion in 'Headphone Amps (full-size)' started by Maxx134, Mar 22, 2019.
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  1. Maxx134
    What I notice on the "tube only" amps, is that most of the tube sound seems to be after the initial transient.
    The thicker harmonics and decay.

    Also what was surprising was how (because of the traditional tube designs) significant the capacitors played a part in the sound of those other amps.
    It was a pain to have to worry about the capacitors as much as the tubes.

    As an example, I went thru at least three brands of cathode caps when upgrading the EC Aficionado to get most transparent sound.
    And that wasn't even dealing with the larger choice of coupling caps.
    In the end I resorted to the stock choice brand, at a higher voltag ratings for upgrading.

    So you see other traditional designs rely heavily on designer experience to get all the "ingredients" to play nice together.
    Its not as simple as some "Splice" circuit simulation, for most tube circuit designs.

    In contrast, see this hybrid design (in these new amps) as forcing all the parts to "behave" in the real world, as in a circuit simulation.
    Last edited: Apr 22, 2019
  2. halcyon
    Very interesting. Any plans on getting the unit objectively measured and posting the results? Yes, the proof is in the pudding (sound), but as a hobbyist it is always also interesting to see the measurements.
  3. SonicTrance
    You mean THD and frequency response? Not really. I was thinking about buying some test gear to test THD but I don't know. I can measure frequency response though just by measuring the output amplitude and vary the input frequency. It's dead flat from 400Hz and up and varies some (not much) under 400Hz. I haven't made any nice graphs for you to look at though.
    But I agree it would be interesting!
    Last edited: Apr 24, 2019
  4. Maxx134
    there is no other proof in the pudding for me.
    Most amplifier measurements mean nothing to the average buyer.
    That plus it is doctored to look good anyways.
    Whatever measurements you can get from this amplifier will easily "look" superior to most tube amps, simply because of the harmonic distortion in tubes, in comparison to this hybrid.

    Normal measurements will not tell you anything.
    Many amplifiers post basic run-of-the-mill measurements which tell you nothing.

    If anything, a more fair or worthy comparison would be to check another hybrid or solid state amp.
    Then get the same measurements it has listed.
    So thats were SonicTrance could look, if he wanted.

    What specific measurement did you want to focus on?
    And from which amp has any posted?

    As far as Im concerned, my methodology of comparison is final proof for me.
    Those that want to look at numbers that's their prerogative. To each his own.

    Of greater interest would be for me, the measurements involved on the topology.
    How it all works.
    Last edited: Apr 24, 2019
  5. Thenewguy007
    How many watts into 300ohms does it put out?
  6. SonicTrance
    I haven't measured that. Its about 1.5w peak into 4 ohms and then gradually lower power output with easier loads (higher impedance loads). Both Oblivion and Citadel have low output impedance of a few ohms. I can assure you that it has no problem driving 300 ohm headphones. People are reporting great things with HD800 for example.

    If youre really interested I can do some measurements at 300 ohm loads?
  7. Thenewguy007
    Well I was wonder how loud the volume can be for the HD800 to max it out.

    Would it the volume knob be at max for that or would it be at the 12 O'clock or 3 O'clock positions etc..?
  8. SonicTrance
    If you have the volume knob anywhere past 12 o'clock your ears would not be happy using those headphones.

    You mean gain, not power.
    Gain is how much you have to turn the volume knob to reach a certain volume, i.e. how much the amp amplifies.

    Power is how much clean signal headroom you have before the amp starts to clip and distort.
    So, an amp with more gain and same power output will clip sooner on the volume dail if that makes sense?
    omniweltall likes this.
  9. Maxx134
    Good idea. I will get out my HD800 tonight hopefully and let you know.
    I remember it pushing the LCD3 very loud before midway, so the question is how loud can you handle it.

    New pics of production versions on second post of first page.
    Last edited: Apr 29, 2019
  10. Thenewguy007
    I'm not familiar with the tubes, but are any of them drop in replacements like EL84, 6h30p or 6922 tubes?
    Just in case someone wants to do a wider assortment of tube rolling?
    Last edited: Apr 29, 2019
  11. SonicTrance
    There’s no tube rolling in these amps other than different makes of the same tube type. As long as the tubes are in good health, with linear curves, you should not notice a big difference when rolling tubes with this topology. The cheapest tubes sounds as good as expensive audiophile tubes in this circuit.
  12. Benny-x
    I hope this isn't a shithead question, but I was wondering if anyone could share how the internal VU meter buffer amps and DC supplies were implemented?

    I am building a pre-amp now based on Bent Audio AVC-1, passive autoformers + the relevant PCBs and I want to add a pair of Hoyt, 3.5” VU meters, but that means I need to add and figure where/how to add buffer amps for the meter signal and DC supplies for the buffers.

    I know that's totally off topic, but I've been following you guys in the old Littledot thread since the beginning and now here, and hope you might be able to share some advice to a novice DIiYer like me.
  13. SonicTrance
    I don’t use VU meters in these amps. The meters measures the bias current of the output tubes. No additional circuit required for that.
    I did use VU meters in a couple other amps I built and just used those Chinese driver boards from eBay. As far as DC supply’s you need a separate winding from your PT then rectify and filter it.
  14. Benny-x
    Haha, I jumped at the shape of them, but should have known they were for bias.

    Thanks for your info. I was recommended this VU meter driver board, but I have no idea whether it's the right/best approach.

    Can you take a look and just let me hear your take on it?
  15. SonicTrance
    My guess is you're fine with that driver board. The thing is that the output of the board needs to work with the meters. Look at the the meter specs. But you had adjustment trimmers on the board so should be fine.
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